Pumps that are useful in the semi-conductor manufacturing industry must be capable of transferring high purity process fluids that are oftentimes corrosive and/or caustic. These high purity process fluids are oftentimes heated to temperatures near their boiling point to increase their efficiency in performing the particular semiconductor manufacturing process. Accordingly, it is important that pumps placed into service with such process fluids be capable of transferring such corrosive and/or caustic process fluids under high-temperature conditions without failing. It is also important that pumps placed into such service do not introduce contaminant matter that can be transferred downstream, which could eventually damage or contaminate the high-purity finished product, e.g., semiconductors and the like.
Conventional pumps that are well known for their application in other less demanding applications are not well suited for use in applications where maintaining the high purity of the process fluid is important. For example, rotary or centrifugal pumps, that rely on the use of a rotating impeller to increase the output pressure of fluid entering the pump, are not well suited for use in high-purity systems because of the potential for the process fluid to come into contact with the impeller bearings upon failure of the bearing packing or pump seal. Exposing the process fluid to the bearings introduces contamination leaving the pump in the form of metal particles, into the process fluid resulting in contamination of the final product. Also, reciprocating piston-type pumps that use dynamic seals around the piston circumference are similarly unsuited for high-purity applications because of the abrasion and wear that occurs at the dynamic piston seal, which results in particulate matter from the worn and abraded seal entering and contaminating the process fluid.
Pumps that have been used in such high-purity service with some degree of success include both diaphragm- and bellows-type pumps. Diaphragm pumps rely on the reciprocating movement of a flexible diaphragm within a chamber to both receive and discharge at pressure the process fluid. The diaphragm for such service can be made from a chemically inert material and is usually fixed about a circumferential edge along the pressure chamber wall. The pressure chamber is configured having inlet and outlet ports that are fitted with one-way check valves so that moving the center portion of the diaphragm in one direction causes fluid to enter the chamber via the inlet port, and moving the diaphragm in the opposite direction causes fluid to exit the chamber via the outlet port. The resulting pressure output produced by the diaphragm pump fluctuates from zero to some desired level, and is not flat. The diaphragm in a diaphragm pump is attached to the pump housing about a peripheral edge, and is attached to an actuating piston by a hole disposed through a center portion of the diaphragm body. This hole serves as an additional leak path, other than that provided at the peripheral seal, for the migration of process fluid past the diaphragm and into the inner workings of the pump where it can be exposed to particulate or other contaminate matter. Fluid passing back through the leak path from the housing can thereby contaminate the remaining process fluid.
Further, the reciprocating movement of the diaphragm is known to place large stresses both upon unsupported areas of the diaphragm and at the point of attachment with the chamber, causing the diaphragm to ultimately fail by rupture or collapse after a relatively short service time. Diaphragm failure not only terminates process fluid transfer but also exposes the process fluid to metallic surfaces and metal particles from parts used to move the diaphragm, e.g., the piston rod, rod bearing and the like, contaminating the high-purity process and possibly contaminating the final product.
Bellows-type pumps rely on the reciprocating movement of a piston-shaped bellows within a closed chamber to both receive process fluid into a pressure chamber and discharge it under pressure. The bellows can be formed from a chemically inert material and is attached along a circumferential skirt to the chamber wall. The advantage of a bellows pressurizing member over a diaphragm is that in theory the bellows is not stressed to the same degree as a diaphragm during reciprocating movement. Rather, the bellows moves within the chamber by the expansion and contraction of its accordion-like cylindrical wall. However, the bellows pump, like the diaphragm pump, also does not have a relatively flat or constant output pressure.
It is also known that the accordion-like cylindrical wall of the bellows is prone to fatigue and failure due to wall thickness nonuniformnities that are inherent in the bellows manufacturing process. Such wall thickness nonuniformities cause the thinnest portion of the accordion-like cylindrical wall to flex the most during reciprocating movement, and ultimately fail due to fatigue stress, thereby limiting the service life of the pump. To ensure accordion-like expansion and contraction movement, and to prevent collapse of the cylindrical wall, the bellows can be supported along the inside wall surface by metal windings. The metal windings prevent the cylindrical wall from collapsing during reciprocating movement. However, upon failure of the accordion-like cylindrical wall, process fluid is free to contact the metal windings, thereby contaminating the process.
Additionally, pumps are used in the semi-conductor manufacturing industry to transport a ultrapure slurry comprising abrasive particles in suspension for such grinding and polishing operations as chemical mechanical planarization. Convention pumps that are used to transport such abrasive slurries are prone to failure caused by the abrasion of the pump wetted surfaces by the slurry material. Typically, the pressurizing member of conventional diaphragm pumps used in slurry transport service undergoes accelerated abrasive wear due to contact with the slurry abrasive particulate matter. Pumps constructed having one or more dynamic seal are also known to fail due to accelerated abrasion wear along the dynamic seal surface. The abrasive wear of such pump components in contact with the slurry material not only cause the pump to fail within a shortened service life, but introduce contaminate material into the ultrapure slurry material being transported, thereby introducing contaminate material into the downstream processes and onto the object being manufactured. Once the pump fails or the system becomes contaminated by abraded pump components, the process must be shut down, the pump repaired, and the system flushed, thereby adding undesired time and cost to the manufacturing process.
It is, therefore, desirable that a pump be constructed that is capable of pressurizing both high and low temperature high-purity process fluid without the possibility of fluid contamination. It is desirable that the pump be constructed in a manner that both minimizes the possibility of internal leakage and is capable of providing an indication of internal leakage. It is desired that the pump be constructed to function in slurry transport service and have an extended service life when compared to conventional pumps subjected to such service. It is also desired that the pump be capable of being operated to provide a substantially constant output pressure, or a pump system be constructed of a plurality of such pumps that is capable of providing a relatively constant overall pressure output and be fault tolerant, i.e., capable of adjusting system operation to maintain a relatively constant discharge pressure when internal pump leakage is detected.